In an organic light emitting diode display device, ambient light can be reflected on the surfaces of a light emitting layer and a metal electrode. When the external background light is strong, part of the reflected light enters the eyes of an observer, so that the contrast of display parts is obviously reduced and the display effect of a display is influenced.
FIG. 1 is a structural schematic diagram of a a top emission display panel of an organic light emitting diode display device in the prior art, including a first substrate 1 and a second substrate 11 which are oppositely arranged; the first substrate 1 includes a plurality of pixel regions 12 and pixel defining regions 13, each of which is located between adjacent pixel regions 12; each of the pixel regions 12 includes an anode 2, an organic light emitting functional layer 14 and a cathode 8 which are successively arranged on the first substrate 1, and the light emitted by the organic light emitting functional layer 14 is sent out from the second substrate 11 (denoted by arrows in FIG. 1); each of the pixel defining regions 13 includes a pixel defining layer 6 arranged on the first substrate 1.
The cathode 8 covers the organic light emitting functional layer 14 and the pixel defining layer 6, and a buffer layer 9 is arranged on the cathode 8, and the buffer layer 9 is in contact with the second substrate 11.
In general, the organic light emitting functional layer 14 includes a first functional layer 3 (generally including a hole injection layer and an electron transport layer) connected with the anode 2, a light emitting layer 4 for emitting light, and a second functional layer 5 (generally including an electron transport layer and an electron injection layer) connected with the cathode.
After entering the second substrate 11, external ambient light can be reflected on the surfaces of the organic light emitting functional layer 14 and the cathode 8. When the external ambient light is strong, part of the reflected light enters the eyes of an observer so that the contrast of display parts is obviously reduced and the display effect of a display is influenced.
In the prior art, a ¼ wavelength polaroid is attached to the surface of the display parts to reduce the reflection on the surfaces of organic light emitting diode devices. By adopting this method, the contrast can be increased, but 60% of emitted light is absorbed or lost by the ¼ wavelength polaroid, and the cost of the polaroid is high.
Secondly, there is also a technology of adding an extinction interference layer to an organic light emitting display device in the prior art, which can also increase the contrast, but a matching relationship between highest occupied molecular orbital energy level and lowest unoccupied molecular orbital energy level of the extinction interference layer and other layer has to be considered.
Thirdly, there is also a technology of adding a light absorption layer to a display device in the prior art, which can reduce reflection of ambient light after entering the interior of the display device, but the light emitted by organic light emitting diode devices is absorbed partially at the same time, so improvement on the contrast of the display device is not obvious.